In various gold plating processes, one or more substrates to be gold plated are mounted in an elecroplating cell in spaced relationship with one or more anodes. A liquid electrolyte is circulated between the cathode(s) and anode(s), an electropotential is applied between the cathode(s) and anode(s) and gold is plated out of the liquid electrolyte into selected areas of the cathode(s). The amount of gold being plated in any particular selected area is dependent upon the current density in that area.
While such gold plating can be effected in a cell in which is mounted only one anode and only one cathode, it is more cost efficient to use the technique known as box plating in which a plurality of cathode articles are simultaneously plated in the same cell. The employment of box plating creates, however, the problem of nonuniform plating of the several cathode substrates. Various proposals to alleviate this problem have been made. Thus, for example, U.S. Pat. No. 3,470,082 issued Sept. 30, 1969 in the name of Raymond et al, and incorporated herein by reference, discloses a box plating apparatus in which there is provided for the plurality of cathodes a respectively corresponding plurality of direct current sources which are mutually independent and electrically isolated from each other, and of which each is connected to the cathode respective thereto such that the current through that cathode can be individually controlled by adjustment of an associated potentiometer without affecting the current through the other cathodes. The Raymond et al. system has, however, the disadvantage that the number of separate current sources required must equal the number of cathodes, and so may become large in number and thereby expensive if the number of cathodes is large. Another disadvantage, without restriction, of the Raymond et al. system is that the device for adjusting the current through each cathode is connected to the current source therefor on the cathode side thereof. Moreover, Raymond et al. fail to disclose a system for providing cathode current control in the instance where the box plating apparatus employs a plurality of anodes and a twice-as-large plurality of cathodes of which a pair thereof are disposed on opposite sides of each anode.